This invention relates to a method of controlling environmental conditions in the proximity of vegetation or crops in the cultivation of plants with the aid of one or more articles of manufacture in the form of protective sheets of plastics material, said sheets being provided with perforations, each perforation having a protruded rim.
The use of protective sheeting made of plastics material provided with perforations having a protruded rim as covering for cold-ground cultures, haystacks etc. is known from DE-B-1 163 596. Described is a foil and its use wherein the foil is provided with a relatively small number of perforations of relatively large dimensions whereby each perforation shows a rim which projects out of the plane of the sheeting. This foil can be used, with the perforations pointing outwards, to cover haystacks to promote drying thereof and to prevent humidification by rain.
The main purpose of such known foil however seems to be a uniform supply of air and water to the soil and to prevent at the same time excessive evaporation of soil moisture. The latter is reached by the fact that condensation of moisture will occur at the inside of a foil covering a culture area, the foil having its projections pointing inwards, and that upon saturation the condensate will be guided by the projections to flow back to the soil. Condensation of water vapour on such a material will result in drop-formation first, if the drop-formation is excessive the flowing back of water will be observed. The presence of condensate in dropform is a serious drawback as the light-transmittance is thereby reduced; such a reduction has a marked influence on the growth of the plants.
Such known foil is described to be used for open air applications only; no indication is given of its use in greenhouse cultivation. If such foil were used in greenhouse cultivation, the problem of light transmittance reduction upon condensation of water vapour would also exist. Further in greenhouse acultivation, control of humidity, temperature and luminance in times of intense sunshine is of great importance. The use of such known foil having a relatively small number of relatively large openings for the purposes as indicated does not offer any advantage.
The present invention has as a goal to provide a method as is indicated in which a plastics protective sheeting is used whereby for above given drawbacks a solution is provided and which foil may be used with advantage both in cold ground applications and in greenhouse applications.